Aluminum electrolyte capacitor with reduced inductivity

ABSTRACT

An aluminum electrolyte capacitor with reduced inductivity is installed in a metal housing that is closed by a cover disk provided with metallic lead-throughs. Electrically conductive bodies are arranged at the cover disk at a region of high magnetic fields when current flows.

BACKGROUND OF THE INVENTION

The invention is directed to an aluminum electrolyte capacitor withreduced inductivity that is installed in a metal housing that is closedby a cover disk provided with metallic lead-throughs.

At high operating frequencies, aluminum electrolyte capacitors have ahigh impedance due to an inductive portion, the impedance being capableof deteriorating the electrical function of the capacitor in thecircuit.

In order to reduce the inductive portion in the electrolyte capacitor,the electrical connections between the capacitor winding and theelectrical lead-throughs in special electrolyte capacitors are designedsuch that the spatial distance between the two lines is minimal. Themagnetic field that arises when a current flows is thus likewiseminimal. Due to the high fabrication-oriented expense and the high costsconnected therewith that arise from this solution, this technicalapproach is not very common in large round can electrolyte capacitors.

SUMMARY OF THE INVENTION

An object of the present invention is to specify an aluminum electrolytecapacitor with reduced inductivity that can be manufactured without highfabrication-oriented expense and in a beneficial manner.

According to the present invention, electrically conductive bodies arearranged at the cover disk, preferably in the region of high magneticfields given a current flow.

The advantage is thereby achieved that currents (eddy currents) areproduced in the conductive bodies by counter-induction, the currentsweakening the alternating magnetic field. As a result thereof, theinductivity of the electrolyte capacitor is reduced.

The invention is explained in greater detail on the basis of thefollowing exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a capacitor cover with conductive bodies on theinside; and

FIG. 2 shows a capacitor cover with conductive bodies on the outside.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to two preferred embodimentsillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended, such alterations andfurther modifications in the illustrated devices and methods, and suchfurther applications of the principles of the invention as illustratedtherein being contemplated as would normally occur to one skilled in theart to which the invention relates.

FIG. 1 shows a cover 1 that, with a terminating disk, closes a capacitorhousing (not shown in FIG. 1). The cover 1 preferably comprises aninsulating plastic and has, for example, a joining piece 2 that isintroduced onto a core hole of the capacitor winding 3 and thus centersthe winding 3. Lead-throughs 4 are arranged in the cover 1, the terminalribbons 5 of the capacitor winding 3 being secured thereto at the insidewith rivets 6.

The magnetic fields within the electrolyte capacitor between the coverdisk 1 and the capacitor winding 3 are at a maximum between the terminalribbons 5. This cavity is therefore filled with conductive bodies 7. Sothat the quality of the electrolyte capacitor is not deteriorated, thesebodies 7 comprise pure aluminum. However, it is also possible that thebodies 7 comprise a conductive plastic that is neutral with respect tothe electrolyte. It is also possible to design the bodies 7 as hollowmembers.

So that the standard cover disks 1 need not be modified, only the twocavities next to the joining piece 2 that separate the plus and minusregion of the electrolyte capacitor from one another are initiallyfilled with conductive bodies 7 in the embodiment of FIG. 1. However, itis also possible that conductive bodies are also arranged at the otherside of the lead-throughs 4.

Another exemplary embodiment of a cover disk 1 provides that thecavities between the lead-throughs 4 at the outside are filled. Thisoccurs with a metal disk a surface of which has an electricalinsulation, so that no tracking currents can arise between thelead-throughs 4. The disk is shaped such that the region between thelead-throughs 4 is nearly completely filled.

Another improvement according to the further exemplary embodiment ofFIG. 2 is achieved by the complete embrace of the lead-throughs 4 abovethe cover disk 1 since eddy currents that are generated by the outsidewiring are thus also enabled, so that a lowering of the overallinductivity results therefrom. Here, too, the metal disk 8 has anelectrical insulation on its surface 9.

The following inductivities were measured at 4 MHz at an aluminumelectrolyte capacitor having a diameter of 75 mm and a height of 145 mm:14.0 nH without disk between the terminals and without conductive bodiesin the electrolyte capacitor and 11.3 nH with conductive bodies in theelectrolyte capacitor. 12.5 nH with a disk between the terminals andwithout conductive bodies in the electrolyte capacitor and 9.5 nH withconductive bodies in the electrolyte capacitor.

By employing at least one conductive body in addition to thecommercially available terminating disk 1, thus the inductivity can belowered by one-third. The inductivity can be lowered further (<50%) byenlarging the conductive parts, this being possible by integration ofthese metal parts into the disk (as inlay parts when injecting thedisk).

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

What is claimed is:
 1. An aluminum electrolyte capacitor with reducedinductivity, comprising: a capacitor winding installed in a metalhousing that is closed by a cover disk; metallic lead-throughs passingthrough the cover disc; and at least one electrically conductive bodyelectrically isolated with respect to the lead-throughs and arranged atat least one of above and below a planar lateral surface of the coverdisk in a region of magnetic fields when current flows.
 2. The aluminumelectrolyte capacitor according to claim 1 wherein the at least oneelectrically conductive body is arranged between the lead throughs. 3.The aluminum electrolyte capacitor according to claim 1 wherein the atleast one electrically conductive body comprises aluminum.
 4. Thealuminum electrolyte capacitor according to claim 1 wherein the at leastone electrically conductive body comprises a conductive plastic that isneutral with respect to an operating electrolyte of the capacitor. 5.The aluminum electrolyte capacitor according to claim 1 wherein the atleast one electrically conductive body is designed as a hollow body. 6.The aluminum electrolyte capacitor according to claim 1 wherein the atleast one electrically conductive body is arranged on an inside of thecover disk between the lead-throughs.
 7. The aluminum electrolytecapacitor according to claim 1 wherein the at least one electricallyconductive body is arranged between the lead-throughs on an outside ofthe cover disk.
 8. The aluminum electrolyte capacitor according to claim7 wherein the at least one electrically conductive body comprises a diskembracing the lead-throughs.
 9. The aluminum electrolyte capacitoraccording to claim 1 wherein two of said electrically conductive bodiesare provided arranged at an inside of the cover disk between thelead-throughs.
 10. The aluminum electrolyte capacitor according to claim9 wherein the two electrically conductive bodies are spaced apart andcentered by an adjoining piece attached as part of the cover disk. 11.The aluminum electrolyte capacitor according to claim 1 wherein the atleast one electrically conductive body comprises a metal disk at a topsurface of said cover disk, said metal disk having respective aperturesfor receiving respective first and second of said lead-throughs.
 12. Analuminum electrolyte capacitor with reduced inductivity, comprising: acapacitor winding installed in a metal housing that is closed by a coverdisk; metallic lead-throughs passing through the cover disk; terminalribbons connecting the respective metallic lead-throughs to thecapacitor winding; and at least one electrically conductive body at aninside lateral surface of the cover disk in a region of magnetic fieldswhen current flows.